Gas! 87 octane vs 91 octane, Ethanol free vs 10% Ethanol?

[BigDaddy13440]

As the title says, who is running what in their Suburban/ Yukon XL or Tahoe/ Yukon?

My Suburban had 143K on it when I got it in June, first couple of tankfuls I ran through it I was getting about 14-14.3 mpg. It's gradually been decreasing, now with 161K and the colder weather I'm down near 12-12.5. Really not too bad, considering I've got turned torsion bars (to level it out), and 285/75/16's. I've had to trim the front air dam by 1 1/2" so the tires wouldn't rub, but otherwise fine.

My biggest issue is what grade gas to use?? I don't believe it has a performance tune in it, but I do notice a slight bit more "pep" when running 91 octane vs 87. But, at 45 cents (or more) per gallon, I know the 91 octane doesn't make a whole lot of sense. At $2.10 a gallon vs $2.55 a gallon, I would have to see an increase from 12 mpg to 14.5 mpg to justify using 91 octane, solely for MPG purposes.

There are ethanol free 91 octane pumps nearby, and I occasionally use that. There is a station in a neighboring city that has all grades of ethanol free gas, but I haven't checked yet to see if they have 93 octane. I did run a tank of 93 octane, and added a quart of Pro 108 Octane Boost to it, noticed more than a bit more grunt....

 

[Walkercraig01]

I run 87 of course it's stock and has 207k on it. Plus... 87 is 1.48 a gallon here

 

[Parthery]

I run 87 in the '08 with the 5.3 and 93 in the '10 with the 6.2 I can feel a noticeable difference in performance.

 

[YukonXL04]

I dont believe the MPG would work out for the cost of 91, When I got my tune I told him I run 87. Wife's Acura runs on 93. we don't have 91 here in Texas really. when we drive through Oklahoma in her car they only have 91 and it definitely runs worse and gets worse mileage compared to out 93 here.

But I have an XL and im not paying an extra 50 cents per gallon for a 31 gallon tank... We dont have the compression to really benefit from it.

 

[01ssreda4]

You're feeling a difference between the fuels because there are two timing tables in the tune, a low and a high. The computer monitors combustion and runs a blend of the two tables, the more octane the more likely you are to be on the higher table.

 

[iLikeEggs]

2011 SSV 132k... . Runs great on 87. I figured that I I won that powerball thing I would start filling it with 89, a then go from a Tall to a Grande a starbuck's (yes, I'm a corporate *****).

 

[OHSIXX]

All I run is premium in mine. I had it tuned by Blackbear for it. Most of the time it has 10% ethanol in it and I see 16-18 mixed driving. I get 14 towing the boat. When I do get out of the city and find a few gas stations that have ethanol free(the good gas) I see about 2-3 MPG's better. Best I've got was 21 on a 4 hour trip back from upnorth(no boat). In the winter I see terrible fuel mileage because they run a winter blend gas and I get 12 or less....fail. Mine is a 6.0 liter w AWD.

 

[nharkey85]

163k miles. Been running 93 for a few months. According to DIC, i got mid 18mpg on a 3.5hr interstate trip running 75mph average. Typically got 14-16mpg with mixed driving

*DIC is skewed due to taller tire, 275/45 22*

 

[VICDBOSS]

If you can get ethanol free, buy it. Putting in higher octane gas when the engine is not tuned for it is a waste of money. I've got 250k miles on my 07 and always ran 87. However try putting in chevron techron concentrate every few thousand miles.


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[BigDaddy13440]

I can honestly say I don't see that much of a difference from running 87 to ethanol free 87 to ethanol free 91.... Worst tank I've had, I averaged about 12.4 mpg (87), best I've had was 13.7 (ethanol free 91).

So I get 10% better mileage, but I've got to pay more than 10% more. Currently, most stations around here average about $2.05 a gallon for 87, with 91 being $2.55. At 25% more for the premium, it financially makes no sense.

Now, if I noticed a big performance gain running the premium, then sure.. but I see very little difference - maybe a touch more low-end off a stop, but otherwise no. And that's running 3-4 tankfulls at each grade, just to allow the computer to adjust.


And as far as running additives.... I've run Seafoam in the tank 3x since June, and have 2 gallons of Lucas fuel treatment I bought, put a quart in about every oil change.